The total number of birds on the planet are difficult to estimate since the number fluctuates seasonally, but an accurate guess would be around 100,000 - 200,000 adult birds in 9,703 species divided in 23 orders and 142 families, from the poles to the tropics.

Red-billed Quelea is known to be the most common wild bird from the south of the Sahara in Africa. Millions of these birds are killed every year to control their numbers. Red Jungle Fowl, which is seen as the common domestic chicken, is the most common bird in all over the world. The European House Sparrow is the most widespread commonly seen wild bird. It has been transported by the European settlers and now you can see them in two thirds of countries, even in Australia, New Zealand, India, Europe and North America.

The heaviest bird, Dromornis Stirtoni from Australia lived some 1-15 million years, was 500 kg and 3m tall. The tallest bird was Dinornus Maximus from New Zealand. The bird with the longest wingspan, 6 meters, is the Giant Teratorn from South America. The smallest bird, 1.6g, is the Bee Hummingbird from Cuba. Another small bird is the little Woodstar from South America. They both fly competently. The smallest bird which cannot fly is the Inaccessible Island Rail. You can find it in the south Atlantic Tristan de Cunha Islands.

When you start to watch birds, one thing you will notice is that they are present only for some of the time; around 1,500 - 4,000 species of birds migrate. Some travel south in winter, some don't. Most of the time this is not migration, but dispersal which is caused by a population boom. This can occur every 4 - 10 years. Another irregular eruption is caused by the destruction or loss of food.

A major factor in many birds life is seasonal migration, involving long distances. It is known that Swifts, Swallows and some small Passerines are migratory birds. You can see them in summer but not in winter. Likewise ducks and geese are only seen in winter in the UK. They return to the north in summer to breed. It is not very well known that some of the regular birds are migrants as well. Robins and Starlings for example, either leave or come to Britain during the winter. In general, birds move to the south. But we never have a time of the year that we do not see any birds around. That's because when some of the birds living in our area migrate to the south, their northern cousins also move to the south to be our guests for the winter. And we enjoy watching these fascinating creatures throughout the year.